Showing papers by "Pramod Kumar Tiwari published in 2016"

Analytical modeling of threshold voltage for symmetrical silicon nano-tube field-effect-transistors (Si-NT FETs)

Abstract: In this paper, an analytical model of the threshold voltage for short-channel symmetrical silicon nano-tube field-effect-transistors (Si-NT FETs) is presented. The three-dimensional (3D) Poisson equation in cylindrical coordinates has been solved with suitable boundary conditions to find the surface potential along the channel length. The inversion charge density $$(Q_{inv} )$$(Qinv) has been calculated in the channel region of the device in the subthreshold regime of device operation, using the Boltzmann relationship. Subsequently, the calculated inversion charge density $$(Q_{inv} )$$(Qinv) has been equated to a threshold charge density $$(Q_{th})$$(Qth) in order to find the threshold voltage $$(V_{th})$$(Vth) expression. The effect of physical device parameters, including the tube thickness, on the threshold voltage and drain induced barrier lowering (DIBL) of the device has been discussed. The model results have been verified with the simulation data obtained by the device simulation software ATLAS.

Cloning & sequence identification of Hsp27 gene and expression analysis of the protein on thermal stress in Lucilia cuprina.

Abstract: Hsp27, a highly conserved small molecular weight heat shock protein, is widely known to be developmentally regulated and heat inducible. Its role in thermotolerance is also implicated. This study is a sequel of our earlier studies to understand the molecular organization of heat shock genes/proteins and their role in development and thermal adaptation in a sheep pest, Lucilia cuprina (blowfly), which exhibits unusually high adaptability to a variety of environmental stresses, including heat and chemicals. In this report our aim was to understand the evolutionary relationship of Lucilia hsp27 gene/protein with those of other species and its role in thermal adaptation. We sequence characterized the Lchsp27 gene (coding region) and analyzed its expression in various larval and adult tissues under normal as well as heat shock conditions. The nucleotide sequence analysis of 678 bps long-coding region of Lchsp27 exhibited closest evolutionary proximity with Drosophila (90.09%), which belongs to the same order, Diptera. Heat shock caused significant enhancement in the expression of Lchsp27 gene in all the larval and adult tissues examined, however, in a tissue specific manner. Significantly, in Malpighian tubules, while the heat-induced level of hsp27 transcript (mRNA) appeared increased as compared to control, the protein level remained unaltered and nuclear localized. We infer that Lchsp27 may have significant role in the maintenance of cellular homeostasis, particularly, during summer months, when the fly remains exposed to high heat in its natural habitat.

Analog and radio-frequency performance analysis of silicon-nanotube MOSFETs

Abstract: This work presents a comparative study of the influence of various parameters on the analog and RF properties of silicon-nanotube MOSFETs and nanowire-based gate-all-around (GAA) MOSFETs. The important analog and RF performance parameters of SiNT FETs and GAA MOSFETs, namely drain current (I d), transconductance to drain current ratio (g m/I d), I on/I off, the cut-off frequency (f T) and the maximum frequency of oscillation (f MAX) are evaluated with the help of Y- and H-parameters which are obtained from a 3-D device simulator, ATLAS™. It is found that the silicon-nanotube MOSFETs have far more superior analog and RF characteristics (g m/I d, f T and f MAX) compared to the nanowire-based gate-all-around GAA MOSFETs. The silicon-nanotube MOSFET shows an improvement of ~2.5 and 3 times in the case of f T and f MAX values respectively compared with the nanowire-based gate-all-around (GAA) MOSFET.

An Analytical Threshold Voltage Model of Fully Depleted (FD) Recessed-Source/Drain (Re-S/D) SOI MOSFETs with Back-Gate Control

Abstract: This paper presents an analytical threshold voltage model for back-gated fully depleted (FD), recessed-source drain silicon-on-insulator metal-oxide-semiconductor field-effect transistors (MOSFETs). Analytical surface potential models have been developed at front and back surfaces of the channel by solving the two-dimensional (2-D) Poisson’s equation in the channel region with appropriate boundary conditions assuming a parabolic potential profile in the transverse direction of the channel. The strong inversion criterion is applied to the front surface potential as well as on the back one in order to find two separate threshold voltages for front and back channels of the device, respectively. The device threshold voltage has been assumed to be associated with the surface that offers a lower threshold voltage. The developed model was analyzed extensively for a variety of device geometry parameters like the oxide and silicon channel thicknesses, the thickness of the source/drain extension in the buried oxide, and the applied bias voltages with back-gate control. The proposed model has been validated by comparing the analytical results with numerical simulation data obtained from ATLAS™, a 2-D device simulator from SILVACO.

Threshold voltage modeling for dual-metal quadruple-gate DMQG MOSFETs

Abstract: In this paper, a three-dimensional 3D model of threshold voltage is presented for dual-metal quadruple-gate metal-oxide-semiconductor field effect transistors. The 3D channel potential is obtained by solving 3D Laplace's equation using an isomorphic polynomial function. Threshold voltage is defined as the gate voltage, at which the integrated charge Qinv at the 'virtual-cathode' reaches to a critical charge Qth. The potential distribution and the threshold voltage are studied with varying the device parameters like gate metal work functions, channel cross-section, oxide thickness, and gate length ratio. Further, the drain-induced barrier lowering has also been analyzed for different gate length ratios. The model results are compared with the numerical simulation results obtained from 3D ATLAS device simulation results. Copyright © 2015 John Wiley & Sons, Ltd.

An analytical gate tunneling current model of Re-S/D SOI MOSFETs

Abstract: This paper presents an analytical direct gate tunneling current model of recessed-source/drain(Re-S/D) SOI MOSFET. The gate tunneling current behavior has been analyzed by varying different parameters like gate insulator thickness and drain to source voltage. The gate tunneling current has been investigated with the effect of high-k dielectric constant. 2D ATLAS tool has been used to validate the model results.

Maintaining the Telomere and its Implication in Cancer

Abstract: Genomic instability has been proposed as one of the emerging hallmarks of cancer. However, molecular mechanisms which cause genomic or chromosomal instability still elude us in various cancers. One of the causes for this genomic instability is dysfunction of the telomere. Telomere dysfunction is associated with an increased risk for different cancers, which results, in principle, due to telomere shortening and loss of telomeric proteins which caps and guard telomeres to distinguish it from double-stranded breaks. In this review, we highlight existing understanding of telomeres, telomerase and their role in cancer progression.